As the blaze in Sydney's south-west remains out of control, fire authorities say giant waterbombing aircraft could have made a difference and they are talking to the Federal Government about additional funding for them outside of bushfire season.

A severe bushfire has burnt all weekend in the Holsworthy area and although conditions eased last night, firefighters are still concerned conditions may deteriorate this afternoon.

The fire, which has ravaged more than 2,400 hectares, continues to burn in a south-easterly direction towards Barden Ridge, but the threat has been reduced and is now at "advice" level.

Residents in Sandy Point, Pleasure Point, Voyager Point, Alfords Point, Barden Ridge, Illawong, Menai and Bangor are all able to return home but are still advised to keep a close eye on the situation and activate their bushfire survival plans if conditions change.

Authorities are concerned about 40 kilometre per hour winds later today and say there is still a lot of work for firefighters to do.

NSW RFS Deputy Commissioner Rob Rogers said two giant aircraft, the DC10 Nancybird and the C130 Hercules "Thor" — normally used for aerial water bombing — were not available to help fight the fire over Saturday and Sunday.

He said the aircraft had already been returned to the United States because they were always sent back by the end of March when temperatures were traditionally cooler.

RFS Commissioner Shane Fitzsimmons said it has to be remembered this blaze is out of fire season but arrangements will be assessed.

"We are working with the Commonwealth about funding strategies that might see our capacity grow to extend," he said.

"It could have made a difference, but ultimately with the 15 or more aircraft we had here the damage has been limited."

Paul Best from the Rural Fire Service said the 250 firefighters currently up against the blaze are cautiously optimistic.

"It's still uncontrolled at the moment but the backburns have gone well," he said.

"There's still an awful amount of work for firefighters to do today ahead of some deteriorating weather conditions."

The RFS said there was very little rain forecast over the next few days across the fire ground and most parts of the state.